Physics Help

[GunnerVIII]

When I did this question I got an answer that seemed a little off. Im not sure if I did something wrong or this was infact the correct answer, anyway the question was:

A rifle can fire a bullet at 1000ms-1. If it is fired vertically into the air, what is the maximum height reached? For how long is it in the air?

I worked out that,

u=1000ms-1
v=0
a=-9.8ms-2
t=?
s=?

I worked out the time first using v=u+at

0=1000-9.8.t
and I got 102 sec

I then worked out the maximum height reached using s=ut+1/2at^2
s=1000.102+1/2.-9.8.102
and I got 51,021 m

Did anyone else get the same answer or have I done something wrong?

Thanks

[greg1917]

yeah. different ways to do it.

since v^2 = u^2 + 2as

you can rearrange to give s = (v^2 - u^2) / 2a

which gives 51020m which is close enough to ure figure.

and yeah v = u + at which gives t as 102s.